Ram shaft assembly for blowout preventer

ABSTRACT

A ram shaft assembly is provided. In one embodiment, a system includes a ram actuation assembly of a blowout preventer. The ram actuation assembly can include a ram shaft, one or more mounting members positioned about the ram shaft, and a piston mounted on the one or more mounting members. Additional systems, devices, and methods are also disclosed.

BACKGROUND

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the presently describedembodiments. This discussion is believed to be helpful in providing thereader with background information to facilitate a better understandingof the various aspects of the present embodiments. Accordingly, itshould be understood that these statements are to be read in this light,and not as admissions of prior art.

In order to meet consumer and industrial demand for natural resources,companies often invest significant amounts of time and money in findingand extracting oil, natural gas, and other subterranean resources fromthe earth. Particularly, once a desired subterranean resource such asoil or natural gas is discovered, drilling and production systems areoften employed to access and extract the resource. These systems may belocated onshore or offshore depending on the location of a desiredresource. Further, such systems generally include a wellhead assemblythrough which the resource is extracted. These wellhead assemblies mayinclude a wide variety of components, such as various casings, valves,fluid conduits, and the like, that control drilling or extractionoperations.

More particularly, wellhead assemblies often include a blowoutpreventer, such as a ram-type blowout preventer that uses one or morepairs of opposing rams that press to one another to restrict flow offluid through the blowout preventer. Many rams include main bodies (orram blocks) that receive sealing elements (or ram packers) that presstogether when a pair of opposing rams close against one another. Often,the rams are driven into and out of a main bore of a blowout preventerby operating pistons coupled to the rams by connecting rods (or ramshafts).

SUMMARY

Certain aspects of some embodiments disclosed herein are set forthbelow. It should be understood that these aspects are presented merelyto provide the reader with a brief summary of certain forms theinvention might take and that these aspects are not intended to limitthe scope of the invention. Indeed, the invention may encompass avariety of aspects that may not be set forth below.

Embodiments of the present disclosure generally relate to ram actuationassemblies for blowout preventers. In some embodiments, a ram actuationassembly includes a ram shaft and a removable piston connected to theram shaft via intermediate mounting members. The mounting members, whichmay be segments of a split mounting ring in one embodiment, arepositioned radially about the ram shaft, such as within an externalgroove of the shaft. The piston is fastened to the mounting members toretain the piston on the ram shaft.

Various refinements of the features noted above may exist in relation tovarious aspects of the present embodiments. Further features may also beincorporated in these various aspects as well. These refinements andadditional features may exist individually or in any combination. Forinstance, various features discussed below in relation to one or more ofthe illustrated embodiments may be incorporated into any of theabove-described aspects of the present disclosure alone or in anycombination. Again, the brief summary presented above is intended onlyto familiarize the reader with certain aspects and contexts of someembodiments without limitation to the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of certain embodimentswill become better understood when the following detailed description isread with reference to the accompanying drawings in which likecharacters represent like parts throughout the drawings, wherein:

FIG. 1 generally depicts a drilling system for forming a well, thedrilling system having wellhead equipment including a blowout preventer,in accordance with one embodiment of the present disclosure;

FIG. 2 is a perspective view of a ram-type blowout preventer having ramactuation assemblies in accordance with one embodiment;

FIG. 3 is a cross-section of the blowout preventer of FIG. 2, whichdepicts the ram actuation assemblies in accordance with one embodiment;

FIGS. 4 and 5 are perspective views of a ram actuation assembly of FIG.3 having a piston coupled to a shaft via one or more intermediatemounting elements in accordance with one embodiment;

FIG. 6 is an elevational view of an end the ram actuation assembly ofFIG. 5 having a ram button;

FIG. 7 is an exploded view generally illustrating positioning ofmounting elements in a groove of the shaft in accordance with oneembodiment;

FIG. 8 is an exploded view generally depicting fastening of the pistonto the mounting elements positioned radially about the shaft inaccordance with one embodiment; and

FIG. 9 is a cross-section of the ram actuation assembly of FIGS. 4 and 5in accordance with one embodiment.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present disclosure will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments, the articles “a,”“an,” “the,” and “said” are intended to mean that there are one or moreof the elements. The terms “comprising,” “including,” and “having” areintended to be inclusive and mean that there may be additional elementsother than the listed elements. Moreover, any use of “top,” “bottom,”“above,” “below,” other directional terms, and variations of these termsis made for convenience, but does not require any particular orientationof the components.

The ram actuation assembly of the present disclosure can be used invarious blowout preventers, and such blowout preventers can be used in avariety of systems. By way of example, a drilling system 10 including ablowout preventer is illustrated in FIG. 1 in accordance with oneembodiment. Notably, the system 10 may be operated to drill a well 12 toaccess a subterranean resource, such as oil or natural gas. As depicted,the system 10 includes an onshore drilling rig 14, although the system10 could instead be an offshore system in other embodiments. Thedrilling rig 14 uses a drill string 16 and a drill bit 18 to form thewell 12.

The drilling rig 14 also includes a mast 20 and a hoisting system (heregenerally shown as including a traveling block 22, a crown block 24, anddrawworks 26) to enable a top drive 28 to be raised and lowered withrespect to a drill floor 30. The drill string 16 is suspended from thetop drive 28, and extends through a hole in the drill floor 30 andthrough wellhead equipment 32 (e.g., a blowout preventer installed on awellhead). The drill string 16 can be rotated by the top drive 28 andcan be raised and lowered with the top drive 28 (via the traveling block22) to facilitate drilling operations. Although the drilling system 10is depicted as including the top drive 28, some other embodiments do notinclude a top drive, such as embodiments using a kelly and a rotarytable for rotating the drill string 16.

One example of a blowout preventer 34 of the wellhead equipment 32 isgenerally depicted in FIGS. 2 and 3. In this embodiment, the blowoutpreventer 34 includes a hollow main body 36 and a bore 38 that allowsfluid or devices (e.g., the drill string 16) to pass through the blowoutpreventer 34. A plate 40 is provided on the main body 36 and can beremoved to allow an operator to easily access the inside of the blowoutpreventer 34. The depicted blowout preventer 34 can be mounted on awellhead or another component by way of a lower connection flange.Additional equipment may be installed on the blowout preventer 34 viastuds on top of the blowout preventer.

Bonnet assemblies 42 secured to the main body 36 include variouscomponents that facilitate control of rams 48 disposed in the blowoutpreventer 34. More specifically, in the depicted embodiment, ramactuation assemblies 50 are disposed in housings between bonnets 44 andend caps 46 of the bonnet assemblies 42. The ram actuation assemblies 50include pistons 52 coupled to ram shafts 54. In operation, a force(e.g., from hydraulic pressure) may be applied to the pistons 52 todrive the rams 48, via the ram shafts 54, into the bore 38 of theblowout preventer 34. The rams 48 can be pipe rams (as depicted in FIG.3) that are driven together to seal about a tubular member (e g., drillstring 16) and inhibit flow through the blowout preventer 34. Such piperams could also include variable-bore pipe rams. But the rams 48 couldtake other forms as well, such as blind rams or shear rams. Further, therams 48 can have any desired size, which may vary depending on theintended application. For example, various pipe rams 48 may be sized foruse with blowout preventers having different bore diameters, such asbores of seven and one-sixteenth inches or nine inches. And in thedepicted embodiment, the end caps 46 include locking stems that can bethreaded through the end caps 46 to engage the ram shafts 54 and lockthe rams 48 into place within the bore 38.

Various ram actuation assemblies can be used to control movement of ramsin a blowout preventer. In one previous instance, ram actuationassemblies included a separable ram shaft with two shaft portions thatcould be coupled together via a threaded connection to retain (e.g.,pin) a piston between the two shaft portions. But a threaded connectionbetween the two shaft portions increases manufacturing expense (e.g.,from machining the threads) and can be susceptible to galling. Further,if the two shaft portions are made of a soft material, like stainlesssteel, care must be taken by an assembler to properly align and connectthe two shaft portions. Otherwise, the threaded surfaces of the twoshaft portions could be scarred, and the actuation assembly could bemisaligned (e.g., out-of-round) when connected. Another previousinstance includes a ram actuation assembly in which the piston is formedintegrally with the ram shaft. While this arrangement may avoid certainalignment issues, manufacturing costs may be undesirably high fromincreased machining time and material expense (e.g., by removingmaterial from stainless steel bar stock, sized to accommodate thelarger-diameter piston, to form the smaller-diameter shaft).

In some embodiments of the present technique, however, the ram actuationassemblies 50 include separate pistons 52 that can be installed on ramshafts 54 without threaded surfaces. Additional details of such ramactuation assemblies 50 may be better understood through reference toFIGS. 4-9, which depict a ram actuation assembly 50 in accordance withcertain embodiments. Perspective views of this example of a ramactuation assembly 50 are provided in FIGS. 4 and 5, while anelevational view of one end of the ram actuation assembly 50 is providedin FIG. 6. These figures show the piston 52 installed on the ram shaft54. One end of the ram shaft 54 (the end depicted in FIG. 6) includes aram button 56 sized to fit within a slot in a ram 48 to facilitatecoupling of the ram shaft 54 to the ram 48, as generally depicted inFIG. 3. The other end of the shaft 54 includes a recess 58 for receivinga locking stem through an end cap 46 as shown in FIG. 3 and discussedabove.

As depicted in the present figures, the ram shaft 54 is formed from asingle piece of material (such as metal), although the shaft could beformed with multiple pieces. More specifically, in at least someembodiments the ram shaft 54 is made from stainless steel bar stock(e.g., type 304 or type 316 stainless steel). And in accordance withcertain embodiments, the depicted ram shaft 54 does not have threadedsurfaces. Compared to certain previous arrangements, the omission ofthreaded connections on the ram shaft 54 in some embodiments allows theram shaft 54 to reduce or avoid the problems of alignment, scarring, andgalling discussed above. And by avoiding the need to cut threads on theshaft, such ram shafts 54 may also be less expensive to manufacture.

The ram actuation assembly 50 also includes one or more mounting members60 for coupling the piston 52 to the ram shaft 54. In FIG. 5, thesemounting members 60 are provided in the form of segments of a splitmounting ring positioned radially about the ram shaft 54. Fasteners 62,such as cap screws, couple the piston 52 to the mounting members 60. Andonce the piston 52 is coupled in this manner it is retained on the ramshaft 54 via the mounting members 60. The piston 52 also includes a seal64 for inhibiting fluid flow between interior portions of a bonnetassembly 42 separated by the piston 52.

The piston 52 and the mounting members 60 can be made from the samematerial as the ram shaft 54 (e.g., stainless steel). But in at leastsome embodiments the piston 52 and the mounting members 60 are made fromdifferent material than the ram shaft 54. For instance, in certainembodiments the ram shaft 54 is made from stainless steel and the piston52 and the mounting members 60 are made from non-stainless steel, suchas a chromoly steel (e.g., type 4130 steel) or a carbon steel. Becausethe piston 52 and mounting members 60 are separate from the ram shaft54, they can be made from less expensive materials than the ram shaft54, thereby reducing manufacturing expense compared to arrangements withram shafts having integral pistons. Maintenance costs may also be lower,as the separate components could be individually replaced as needed.

To assemble the piston 52 and the mounting members 60 on the ram shaft54, the mounting members 60 are first positioned about the ram shaft 54as generally depicted in FIGS. 7 and 8. The mounting members 60 includeinner edges 72, holes 76, and outer edges 78. In this illustratedembodiment, the mounting members 60 are received in an external groove74 of the ram shaft 54.

The piston 52 includes an aperture 80 that allows the piston 52 to beslipped over an end of the ram shaft 54. Once the mounting members 60are positioned about the ram shaft 54, the piston 52 may be moved alongthe ram shaft 54 to engage the mounting members 60. In this position,the piston 52 abuts a seal 70 within a seal groove 68 of the ram shaft54. And like the seal 64, the seal 70 inhibits fluid from passingbetween interior portions of the bonnet assembly 42 separated by thepiston 52. In at least some embodiments, the ram actuation assemblies 50are constructed to use the same seals 64 and 70 as certain previous ramactuation assemblies. This enables a blowout preventer to be retrofitwith ram actuation assemblies 50 that use the same seals as the previousram actuation assemblies.

In the depicted embodiment, the piston 52 includes a recess 82 thatallows the piston 52 to receive the mounting members 60 within therecess 82 such that the piston 52 circumscribes or otherwise encompassesthe outer edges 78 of the mounting members 60. The piston 52 includes ashoulder 84 having threaded mounting recesses 86. In the depictedembodiment, after the mounting members 60 are received in the recess 82,the piston 52 can then be coupled to the mounting members 60 bythreading the fasteners 62 into mounting recesses 86 through the holes76, as generally depicted in FIGS. 8 and 9.

The recess 82 generally facilitates assembly of the piston 52 on the ramshaft 54 by allowing the piston 52 to encircle the split mounting ringsegments or other mounting members 60 and hold them in place about theram shaft 54 while the fasteners 62 are installed. But in otherembodiments, the recess 82 could be omitted. For example, the piston 52could have a flat transverse surface, rather than a recessed surface,that abuts the mounting members 60.

While the aspects of the present disclosure may be susceptible tovarious modifications and alternative forms, specific embodiments havebeen shown by way of example in the drawings and have been described indetail herein. But it should be understood that the invention is notintended to be limited to the particular forms disclosed. Rather, theinvention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by thefollowing appended claims.

1. A system comprising: a ram actuation assembly of a blowout preventer,the ram actuation assembly including: a ram shaft; one or more mountingmembers positioned about the ram shaft; and a piston mounted on the oneor more mounting members.
 2. The system of claim 1, comprising a splitmounting ring including the one or more mounting members.
 3. The systemof claim 1, wherein the piston is connected to the one or more mountingmembers by fasteners inserted through holes in the one or more mountingmembers and into threaded recesses in the piston.
 4. The system of claim1, wherein the one or more mounting members are positioned within agroove of the ram shaft.
 5. The system of claim 1, comprising a sealbetween the piston and the ram shaft.
 6. The system of claim 1, whereinthe one or more mounting members are positioned within a recess of thepiston.
 7. The system of claim 1, wherein the ram shaft does not have athreaded surface.
 8. The system of claim 1, wherein the ram shaft ismade of a different material than the one or more mounting members andthe piston.
 9. The system of claim 8, wherein the ram shaft is made ofstainless steel and each of the one or more mounting members and thepiston is made of non-stainless steel.
 10. The system of claim 1,wherein the ram shaft includes a ram button.
 11. The system of claim 10,comprising a ram installed on the ram button of the ram shaft.
 12. Thesystem of claim 1, comprising the blowout preventer.
 13. A systemcomprising: a ram actuation assembly of a blowout preventer, the ramactuation assembly including a shaft having an external groove, a splitring having multiple segments, and a piston having an aperture toreceive the shaft and a recess configured to encompass the multiplesegments, wherein the multiple segments of the split ring are configuredto be positioned radially about the shaft within the external groove andto enable the piston to be coupled to the shaft via the multiplesegments.
 14. The system of claim 13, wherein the shaft is formed of asingle piece of stainless steel.
 15. The system of claim 13, wherein thepiston is fastened to the multiple segments by a plurality of capscrews.
 16. The system of claim 13, wherein the shaft is receivedthrough the aperture of the piston, the multiple segments are positionedradially about the shaft within the external groove, and the piston iscoupled to the shaft via the multiple segments.
 17. A method comprising:positioning segments of a split mounting ring about a blowout preventerram shaft; and coupling a piston to the segments of the split mountingring such that the piston is connected to the blowout preventer ramshaft via the segments of the split mounting ring.
 18. The method ofclaim 17, wherein coupling the piston to the segments of the splitmounting ring includes receiving the segments of the split mounting ringin a recess of the piston and fastening the segments of the splitmounting ring to the piston.
 19. The method of claim 17, whereinpositioning the segments of the split mounting ring about the blowoutpreventer ram shaft includes positioning the segments in a groove of theblowout preventer ram shaft.
 20. The method of claim 17, comprisingforming the ram shaft from stainless steel bar stock.